Repair of nonreplicating UV-irradiated DNA: cooperative dark repair by Escherichia coli uvr and phr functions

Abstract

The system previously used to study recombination of honreplicating UV-irradiated phage k DNA was adapted to study UV repair. Irradiated phages infected undamaged homoimmune lysogens. Pyrimidine dimer content (by treatment with Micrococcus luteus UV endonuclease and alkaline sucrose sedimentation) and a biological activity endpoint (infectivity in transfection of uvrB recA recB spheroplasts) were followed. Unless room light was excluded during DNA extraction procedures, photoreactivation (Phr function) was significant. In uvr Aphr bacteria, repair, by both assays, was very low but not zero. Even when light was totally excluded, Phr function appeared to play a role in Uvr-mediated excision repair: both dimer removal and restoration of infectivity were two to five times as efficient in uvr+ phr+ bacteria as in uvr+ Aphr bacteria. Similarly, UV-irradiated phages plated with higher efficiencies on phr+ than Aphr bacteria even under totally dark conditions. In uvr phr+ repressed infections, removal of dimers from nonreplicating DNA did not increase infectivity as much as in uvr+ infections, suggesting a requirement for repair of nondimer photoproducts by the uvrABC system.

Two cDNAs from the plantArabidopsis thalianathat partially restore recombination proficiency and DNA-damage resistance toE.colimutants lacking recombination-intermediate-resolution activities

“…Media and solutions TBY-broth, LB-broth-plates, and M9-minimal-plates have been described (26,27). TBY-Ap broth and LB-Ap plates contain 50 /g/ml ampicillin (Ap).…”

Interactions between Yeast Photolyase and Nucleotide Excision Repair Proteins in Saccharomyces cerevisiae and Escherichia coli

“…The light-dependent repair of pyrimidine dimers has long been the sole known function of DNA photolyases. Only recently has evidence been obtained that in E. coli, photolyase also plays a role in the dark repair of dimers; both in vivo and in vitro studies indicate that this role is stimulation of nucleotide excision repair via interaction between photolyase and ABC excision nuclease (12,13,24,31,50,51). In this report, we have presented evidence that photolyase performs a similar function in yeast cells.…”

“…pathway (12,13,50,51). Several years ago, we demonstrated that this characteristic is due to photolyase-mediated enhancement of dimer recognition by ABC excision nuclease (31), which catalyzes the first step in nucleotide excision repair, namely, incision of the damage-containing strand on each side of the lesion (34).…”

Recombinagenic processing of UV-light photoproducts in nonreplicating phage DNA by the Escherichia coli methyl-directed mismatch repair system.

“…Plasmids: pCSR606 encodes the E. coli phr+ gene and some adjacent bacterial genes (SANCAR, SMITH and SANCAR 1983). pGG503 consists of a PstI fragment encoding the E. coli dam+ gene, inserted into pBR322 (HERMAN and MOD-Media and buffers: The following have been described elsewhere (HAYS, MARTIN and BHATIA 1985): TBM, TBMM, TBY and S broths; T A top agar; LBH and TCMB plates; T M , TMG and TS buffers; DNA buffer and extraction buffer. S-plates contain S-broth + 1% agar.…”